Conductive member for OA equipment

ABSTRACT

A conductive member for OA equipment (electrophotographic apparatus or electrostatic recording apparatus) which is obtainable from a composition comprising a non-ether-based polyurethane, carbon black and bis(trifluoromethanesulfonyl)imidolithium. The conductive member shows very stable conductivity in the volume resistivity range of 10 5  to 10 12  Ω·cm, the conductivity of which is less dependent on the voltage applied and varies only slightly during continuous energization and upon changes in environmental factors such as temperature and humidity.

TECHNICAL FIELD

The present invention relates to conductive members for OA equipmentwhich are suitable for blades, rollers and belts for charging,developing, transfer, fixation, static electricity elimination,cleaning, paper feeding or transportation in electrophotographicapparatus and electrostatic recording apparatus such as copiers,facsimile equipment and printers.

BACKGROUND ART

OA equipment including electrophotographic apparatus and electrostaticrecording apparatus such as copiers, facsimile equipment, printers areconstituted of various parts, and blades, rollers and belts areessential parts playing such a roll as charging, developing, transfer,fixation, static electricity elimination, cleaning, paper feeding ortransportation in electrophotographic processes. These parts are mostlymade of polyurethane materials and, in many cases, they must be providedwith a conductivity of about 10⁴ to 10¹² Ω·cm from the functionalviewpoint.

The most popular measures that has so far been taken for providingpolyurethane members for OA equipment parts with conductivity comprisesmolding a polyurethane material prepared by kneading and dispersingcarbon black with and in the polyol constituent, for instance.

However, it is very difficult to provide such moldings wholly anduniformly with stable conductivity by the method comprising dispersing,by kneading, of carbon black, since a slight deviation in the amount ofaddition of such a substance, slight changes in such conditions asmaterial temperature, molding temperature and molding time and, further,the use of a different molding method result in changes in conductivepath morphology, hence in great variations in conductivity, inparticular in the volume resistivity range of 10⁶ to 10¹¹ Ω·cm.

Furthermore, carbon black is generally higher in specific gravity thanpolyurethanes, so that it settles and is distributed unevenly duringmolding and, further according to the moldings morphology, leading todevelopment of faults in conductive paths of carbon black and making itdifficult to stably provide the moldings with uniform conductivity. Thistendency is strong especially with the moldings molded by thecentrifugal molding method in which a great centrifugal force is exertedon the materials. Therefore, to cope with such difficulties, it isindispensable to strictly control the manufacturing conditions accordingto the moldings morphology and/or molding method. Moreover, with theconductive polyurethanes obtained by such methods, the electricresistance is highly dependent on the voltage applied, hindering thedevelopment of high-performance electrophotographic apparatus andelectrostatic recording apparatus.

SUMMARY OF THE INVENTION

In view of the foregoing, it is an object of the present invention toprovide a conductive member for OA equipment which shows very stableconductivity in the volume resistivity range of 10⁵ to 10¹² Ω·cm, theconductivity of which is less dependent on the voltage applied andvaries only slightly during continuous energization and upon changes inenvironmental factors such as temperature and humidity.

The present invention is a conductive member for OA equipment, which isobtainable by molding a composition comprising a non-ether-basedpolyurethane, carbon black andbis(trifluoromethanesulfonyl)imidolithium.

The conductive member for OA equipment according to the presentinvention, which is a conductive blade, a conductive roller or aconductive belt also constitutes an aspect of the present invention alsoconstitutes an aspect of the present invention.

DETAILED DISCLOSURE OF THE INVENTION

In the following, the present invention is described in detail.

The present invention is concerned with a conductive member for OAequipment, which is obtainable by molding a composition comprising anon-ether-based polyurethane, carbon black andbis(trifluoromethanesulfonyl)imidolithium.

As a result of intensive investigations made by them to accomplish theabove-mentioned object, the present inventors found that non-ether-basedpolyurethanes containing carbon black andbis(trifluoromethanesulfonyl)imidolithium combinedly used as conductiveagents show very stable electric resistance in the volume resistivityrange of 10⁵ to 10¹² Ω·cm and their conductivity does not greatly dependon the voltage. These findings have now led to completion of the presentinvention.

The composition to be used the present invention comprises anon-ether-based polyurethane, carbon black andbis(trifluoromethanesulfonyl)imidolithium. The term “non-ether-basedpolyurethane” as used herein means the product of the reaction between anon-ether-based polyol and a polyisocyanate.

The above non-ether-based polyol includes, for example, condensationpolymer type polyester polyols such as typically poly(ethylene adipate)polyol, poly(butylene adipate) polyol, and poly(ethylene butyleneadipate) polyol; lactone-derived polyester polyols such as typicallypoly(caprolactone) polyol and poly(β-methyl-γ-valerolactone) polyol;olefin-derived polyols such as typically poly(isoprene) polyol andpoly(butadiene) polyol; poly(carbonate) polyols, castor oil-basedpolyols, acrylic polyols, dimer acid polyols, silicone-based polyols,fluorine-containing polyols, etc.

Incidentally, ether type polyols such as typically polyethylene glycoland poly(oxytetramethylene) glycol, are highly hygroscopic and increasethe environment dependency of the conductivity, hence are unsuited foruse in producing conductive members for OA equipment according to thepresent invention.

The above-mentioned polyisocyanate is not particularly restricted butincludes, for example, tolylene diisocyanate (TDI),4,4′-diphenylmethanediisocyanate (MDI), liquid MDI, xylylenediisocyanate (XDI), naphthylene-1,5-diisocyanate (NDI), hexamethylenediisocyanate (HDI), hydrogenated TDI, hydrogenated MDI,isophoronediisocyanate (IPDI), lysinediisocyanate (LDI),isopropylidenebis(4-cyclohexyl isocyanate), norbornanediisocyanate andthe like.

In reacting the above non-ether-based polyol with the abovepolyisocyanate, a curing agent may be added.

The curing agent is not particularly restricted but includes, forexample, aliphatic, aromatic, alicyclic and heterocycliclow-molecular-weight glycols; triols such as trimethylolpropane andglycerin; polyhydric alcohols such as pentaerythritol and sorbitol; andamine compounds, typically methylenebis-o-chloroaniline (MOCA).

The feature of the present invention comprises in using carbon black andbis(trifluoromethanesulfonyl)imidolithium represented by the formulashown below combinedly as conductive agents.

 LiN(SO₂CF₃)₂

The above-mentioned carbon black is not particularly restricted butincludes, for example, furnace black species such as typically Ketjenblack EC and Valcan XC-72; acetylene black, acidic carbon black, andgrafted carbon species resulting from grafting of a polymer on thecarbon particle surface. These species may be used singly or two or moreof them may be used in combination.

In the present invention, carbon black is dispersed in a polyol bykneading. The amount of carbon black to be dispersed in the polyol bykneading is preferably at most 10% by weight based on the wholecomposition. When it exceeds 10% by weight, the viscosity of the polyolbecomes markedly high, making it difficult to conduct the molding and/ordehydration and defoaming procedure.

In accordance with the present invention,bis(trifluoromethanesulfonyl)imidolithium is used as a conductive agentin addition to carbon black. Bis(trifluoromethanesulfonyl)imidolithiumis preferably used in an amount within the range of 0.01 to 200% byweight relative to the amount of carbon black used in combination. Whenit is less than 0.01% by weight, the stability of conductivity will beimpaired and the variation in electric resistance value will increase.On the other hand, when it exceeds 200% by weight, no more improvementin resistance stability will be produced.

In accordance with the present invention, it has been so designed thateven when defects are produced in electronically conductive paths of theconductive substance carbon black, the ionic conductive substancebis(trifluoromethanesulfonyl)imidolithium can complement them.Therefore, it is possible to provide the moldings with a desired levelof conductivity, irrespective of molding method and without strictlycontrolling the manufacturing conditions.

The conductive member for OA equipment according to the presentinvention is molded from the above-mentioned composition.

The above-mentioned composition comprises a non-ether-based polyurethaneand bis(trifluoromethanesulfonyl)imidolithium and preferably essentiallyconsists of a non-ether-based polyurethane andbis(trifluoromethanesulfonyl)imidolithium.

In molding the above composition to obtain the conductive member for OAequipment, a catalyst may be added to the above composition forpromoting the curing reaction.

The catalyst is not particularly restricted but may be any of thesubstances promoting the urethane formation reaction. Thus, suchcatalysts as amine compounds and organometallic compounds, which aregenerally used in urethane formation, can be used.

The method for molding of the conductive member for OA equipment is notparticularly restricted but includes, for example, ordinary pressurecasting molding, reduced pressure casting molding, centrifugal molding,rotational molding, extrusion molding, injection molding, reactioninjection molding (RIM), and spin coating.

The conductive member for OA equipment according to the presentinvention may serve as any conductive member to be used in OA equipment,without any particular restriction. As such member, there may bementioned, for example, conductive blades, conductive rollers,conductive belts and the like. Such a conductive blade, conductiveroller or conductive belt also constitutes an aspect of the presentinvention.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be described in more detail by way ofexamples, but the present invention is not restricted only to theseexamples.

EXAMPLE 1

Poly(ethylene butylene adipate) polyol having an average molecularweight of 2,000 and a number of functional groups of 2 and containing aconductive carbon black species (Ketjen black ECP) dispersed therein bykneading as dehydrated and defoamed as a whole by warming under reducedpressure, a prepolymer prepared by reacting poly(ethylene butyleneadipate) polyol having an average molecular weight of 2,000 and a numberof functional groups of 2 with MDI to attain an NCO content of 16%, anda curing agent comprising a mixture of 1,4-butanediol andtrimethylolpropane in a weight ratio of 7:3 and containingbis(trifluoromethanesulfonyl)imidolithium dissolved therein in advancewere weighed in respective amounts such that the ratio: number of molesof the hydroxyl group in the poly(ethylene butylenes adipate) polyolwith carbon black dispersed therein/number of moles of the isocyanatogroup in the prepolymer/number of moles of the hydroxyl group in thecuring agent amounted to 1:2.7:1.6 and, after mixing up of these withstirring, the mixture was cured in a centrifugal molding machine at 130°C. for about 1 hour. Then, the molding was taken out of the centrifugalmolding machine and matured at room temperature for 12 hours to give asheet-like sample with a thickness of 2 mm. The amount of addition ofbis(trifluoromethanesulfonyl)imidolithium was 70% by weight relative tothat of carbon black.

EXAMPLE 2

A sample was prepared in the same manner as in Example 1 except that theamount of addition of bis(trifluoromethanesulfonyl)imidolithium was 145%by weight relative to that of carbon black.

EXAMPLE 3

A sample was prepared in the same manner as in Example 1 except that theamount of addition of bis(trifluoromethanesulfonyl)imidolithium was 0.2%by weight relative to that of carbon black.

EXAMPLE 4

Poly(ethylene butylene adipate) polyol having an average molecularweight of 2,000 and a number of functional groups of 2 and containing aconductive carbon black species (Ketjen black ECP) dispersed therein bykneading as dehydrated and defoamed as a whole by warming under reducedpressure, liquid MDI as a polyisocyanate component, and a curing agentcomprising a mixture of 1,4-butanediol and trimethylolpropane in aweight ratio of 7:3 and containingbis(trifluoromethanesulfonyl)imidolithium dissolved therein in advancein respective amounts such that the ratio: number of moles of thehydroxyl group in the poly(ethylene butylene adipate) polyol with carbonblack dispersed therein/number of moles of the isocyanato group in thepolyisocyanate/number of moles of the hydroxyl group in the curing agentamounted to 1:3.2:2.1 were added in a one-shot manner and, after mixingup with stirring, the mixture was cured in a centrifugal molding machineat 130° C. for about 1 hour. Then, the molding was taken out of thecentrifugal molding machine and matured at room temperature for 12 hoursto give a sheet-like sample with a thickness of 2 mm. The amount ofaddition of bis(trifluoromethanesulfonyl)imidolithium was 70% by weightrelative to that of carbon black.

EXAMPLE 5

The same compound as used in Example 1 was manually cast into a moldhaving a 2-mm-thick spacer and maintained at 130° C. and cured at thattemperature for about 1 hour. The molding was then taken out of the moldand matured at room temperature for 12 hours to give a sheet-like samplewith a thickness of 2 mm.

COMPARATIVE EXAMPLE 1

Poly(ethylene butylene adipate) polyol having an average molecularweight of 2,000 and a number of functional groups of 2 and containingthe same amount as used in Example 1 of a conductive carbon blackspecies (Ketjen black ECP) dispersed therein by kneading as dehydratedand defoamed as a whole by warming under reduced pressure, a prepolymerprepared by reacting poly(ethylene butylene adipate) polyol having anaverage molecular weight of 2,000 and a number of functional groups of 2with MDI to attain an NCO content of 16%, and a curing agent comprisinga mixture of 1,4-butanediol and trimethylolpropane in a weight ratio of7:3 were weighed in respective amounts such that the ratio:number ofmoles of the hydroxyl group in the poly(ethylene butylene adipate)polyol with carbon black dispersed therein/number of moles of theisocyanato group in the prepolymer/number of moles of the hydroxyl groupin the curing agent amounted to 1:2.7:1.6 and, after mixing up thereofwith stirring, the mixture was cured in a centrifugal molding machine at130° C. for about 1 hour. Then, the molding was taken out of thecentrifugal molding machine and matured at room temperature for 12 hoursto give a sheet-like sample with a thickness of 2 mm.

COMPARATIVE EXAMPLE 2

A sheet-like sample with a thickness of 2 mm was obtained in the samemanner as in Comparative Example 1 except that the amount of theconductive carbon black (Ketjen black ECP) dispersed was the same as inExample 2.

COMPARATIVE EXAMPLE 3

The same compound as used in Comparative Example 1 was manually castinto a mold having a 2-mm-thick spacer and maintained at 130° C. andcured at that temperature for about 1 hour. Then, the molding was takenout of the mold and matured at room temperature for 12 hours to give asheet-like sample with a thickness of 2 mm.

The samples obtained in Examples 1 to 5 and Comparative Examples 1 to 3were subjected to the following evaluation tests. The results are shownin Table 1.

[Conductivity Evaluation]

Evaluation measurements were made using a resistance measuring apparatus(model R8340A, produced by Advantest Corp.).

(1) Volume Resistivity

Each sample was evaluated for volume resistivity by applying a voltageof 250 V for 30 seconds. Measurements were made at 15 sites all over thesample surface, and the arithmetic mean was reported as the volumeresistivity value.

(2) Variation in Volume Resistivity

The volume resistivity values for the 15 sites as obtained in (1) wereplotted on a logarithmic graph paper each scale mark of whichcorresponded to 1×10^(x) (x represents an integer), and the variationwas evaluated in terms of the difference, in number of scale marks,between the maximum and minimum value.

(3) Voltage Dependency

A voltage of 10 to 1,000 V was applied to each sample for 30 seconds,and the volume resistivity values thus obtained were plotted on alogarithmic graph paper each scale mark of which corresponded to1×10^(x) (x represents an integer), and the dependency was evaluated interms of the difference, in number of scale marks, between the maximumand minimum value.

(4) Changes During Continuous Energization

A voltage of 100 V was applied to each sample continuously for 30seconds, 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes or 30minutes, and resistant measurements were made at 5-minute intervals. Thedata obtained were plotted on a logarithmic graph paper each scale markof which corresponded to 1×10^(x) (x represents an integer), and theevaluation was made in terms of the difference, in number of scalemarks, between the maximum and minimum value.

(5) Changes in the Environment

A voltage of 250 V was applied to each sample for 30 seconds in alow-temperature, low-humidity environment (10° C., 15% relativehumidity) to a high-temperature, high-humidity environment (32.5° C.,85% relative humidity), and the volume resistivity were measured andplotted on a logarithmic graph paper each scale mark of whichcorresponded to 1×10^(x) (x represents an integer). The evaluation wasmade in terms of the difference, in number of scale marks, between themaximum and minimum value.

TABLE 1 Conductivity Volume Variation in Changes during resistivityvolume Voltage continuous Changes in the (Ω · cm) resistivity dependencyenergization environment Example 1 1.7 × 10⁶   3 marks  7 marks  5 marks10 marks Example 2 1.1 × 10¹¹  2 marks  5 marks  3 marks  8 marksExample 3 2.2 × 10⁸   5 marks  9 marks  6 marks 11 marks Example 4 9.2 ×10⁵   4 marks  8 marks  5 marks 11 marks Example 5 1.4 × 10⁶   4 marks 7 marks  4 marks 10 marks Comparative 7.0 × 10⁸  25 marks 60 marks 12marks 30 marks Example 1 Comparative 9.4 × 10¹¹ 50 marks 60 marks 35marks 25 marks Example 2 Comparative 4.3 × 10⁵  15 marks 30 marks 11marks 20 marks Example 3

Industrial Applicability

The present invention, which has the constitution described hereinabove,can provide conductive members for OA equipment which simultaneouslyhave such characteristics as very stable electric resistance in thevolume resistivity range of 10⁵ to 10¹² Ω·cm, slight dependency ofconductivity on voltage, and small changes in conductivity duringcontinuous energization and upon changes in environmental factors suchas temperature and humidity.

1. A conductive member for OA equipment, which is obtainable from acomposition comprising a non-ether-based polyurethane, carbon black andbis(trifluoromethanesulfonyl) imidolithium, wherein said OA equipment iselectrophotographic apparatus or electrostatic recording apparatus. 2.The conductive member for OA equipment according to claim 1, which is aconductive blade.
 3. The conductive member for OA equipment according toclaim 1, which is a conductive roller.
 4. The conductive member for OAequipment according to claim 1, which is a conductive belt.
 5. Theconductive member for OA equipment according to claim 1, wherein saidnon-ether-based polyurethane is the product of the reaction of anon-ether-based polyol, a polyisocyanate, 1,4-butanediol andtrimethylolpropane.
 6. The conductive member for OA equipment accordingto claim 2, wherein said non-ether-based polyurethane is the product ofthe reaction of a non-ether-based polyol, a polyisocyanate,1,4-butanediol and trimethylolpropane.
 7. The conductive member for OAequipment according to claim 3, wherein said non-ether-basedpolyurethane is the product of the reaction of a non-ether-based polyol,a polyisocyanate, 1,4-butanediol and trimethylolpropane.
 8. Theconductive member for OA equipment according to claim 4, wherein saidnon-ether-based polyurethane is the product of the reaction of anon-ether-based polyol, a polyisocyanate, 1,4-butanediol andtrimethylolpropane.
 9. The conductive member for OA equipment accordingto claim 1, which is obtained by centrifugal molding.
 10. The conductivemember for OA equipment according to claim 2, which is obtained bycentrifugal molding.
 11. The conductive member for OA equipmentaccording to claim 3, which is obtained by centrifugal molding.
 12. Theconductive member for OA equipment according to claim 4, which isobtained by centrifugal molding.
 13. The conductive member for OAequipment according to claim 5, which is obtained by centrifugalmolding.
 14. The conductive member for OA equipment according to claim6, which is obtained by centrifugal molding.
 15. The conductive memberfor OA equipment according to claim 7, which is obtained by centrifugalmolding.
 16. The conductive member for OA equipment according to claim8, which is obtained by centrifugal molding.